Deserialization in Creativethemeshq Blocksy

CVE-2026-8365

The Blocksy theme for WordPress is vulnerable to PHP Object Injection leading to Remote Code Execution via the 'blocksy_meta' REST API field and the V200 database migration in versions up to and including 2.1.35. This is due to insufficient input sanitization in the blocksy_sanitize_post_meta_options() function, which only blocks values containing '<' or '>' and does not prevent serialized PHP object strings from being stored in post meta, combined with the SearchReplacer::run_recursively() function unconditionally deserializing all string values via @unserialize() during migration without restricting allowed classes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject a serialized Blocksy\RaiiPattern object into post meta that, when the V200 migration runs on an upgraded site, is deserialized and triggers RaiiPattern::__destruct(), which executes arbitrary PHP callables via call_user_func().

Vulnerability class: Insecure Deserialization

Published · last modified .

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.016 (74.8th percentile), scored .

Low probability of exploitation in the next 30 days, but still tracked. 75th percentile — 74.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-8365: held from 0.011 to 0.016.

EPSS over last 30 days · oldest: 0.011 · newest: 0.016 · change: +0.005

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-8365?
CVE-2026-8365 is a high-severity vulnerability in Creativethemeshq Blocksy, classified under Deserialization of Untrusted Data. CVSS score: 8.8/10. Published 2026-06-09.
How severe is CVE-2026-8365?
High severity. CVSS v3 base score is 8.8 out of 10.